Shut-off valve and sealing ring

ABSTRACT

A shut-off valve includes a housing defining a flow channel and a bore for receiving a rotary actuator, a valve member, and first and second seal rings. The first seal ring cooperates with the valve member to close and seal the flow channel. The second seal ring cooperates with the valve member to seal the actuator bore. The seal rings are composed of radially extending metal lamellae interposed between soft material lamellae. The soft material lamellae are composed of lubricating material having a non-homogeneous structure which have the capacity to form radial freely extending sliding layers. The metal lamellae have, at least in the region around the inside surface of the seal rings, axial deformations. Such axial deformations provide positive mechanical connection to the adjoining soft material lamellae, restricting the soft material sliding layers to at most one third of the lamellae thickness.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to valves having a housing defining aflow channel, an axially displaceable valve member and a pair of sealingor packing rings which cooperate with the valve member to control flowand prevent leakage. More particularly, the present invention relates toshut-off valves having first and second sealing rings and to sealingrings comprised of axially alternating layers of radially extending softmaterial lamellae and metal lamellae, the soft material lamellae havinga non-homogeneous structure.

2. Description of the Prior Art

The soft material lamellae employed in prior art shut-off valves whichemploy a piston-type valve member are typically comprised ofrubber-asbestos (IT) material or expanded graphite. Such soft materialsare nonhomogeneous and consist of particles with interposed voids. Suchvoids prove to be a disadvantage when, in the operation of the valve,the operating system pressure suddenly drops. If such voids are filledwith liquid, the sudden pressure drop may cause the liquid to flash tothe vapor state. When this happens, the sudden increase in the volume ofthe contents of multiple voids results in explosive medium shock waveswhich propagate toward or away from the shell surface, i.e., the axialsurface of the seal ring which contacts the valve member. The shockwaves cause the soft material to flow, displacing parts of the seal ringsealing lamellae. Such relative displacements can result in sealing ringfailure. The likelihood of this failure mode is particularly high invalves located upstream of condensate traps. In order to prevent sealring damage, the addition of metal lamellae between layers of softmaterial lamellae to provide additional strength to the seal ring iswell known in the art. However, such compound seal rings are stillsubject to damage from such explosive medium shocks, the shock wavescausing the soft material lamellae to slide over the adjacent metallamellae, thereby displacing parts of the sealing lamellae.

SUMMARY OF THE INVENTION

The present invention overcomes the above-discussed and otherdeficiencies and disadvantages of the prior art by providing an improvedshut-off valve, wherein a sudden large drop in operating pressure doesnot cause destruction of the sealing ring, and a novel sealingarrangement for use in such a valve.

Briefly stated, the invention in a preferred form is a shut-off valvehaving first and second seal rings composed of alternating layers ofradially extending soft material lamellae and metal lamellae whereinpreformed axial deformations provide positive connection betweenadjoining lamellae. Such positive connection restricts the sliding ofthe soft material lamellae on the metal lamellae upon the occurrence ofexplosive medium shocks.

The axial deformations may be formed in a number of ways and may belocated in various areas of the seal rings. Preferably, the axialdeformations are made in such a way that no relative motion, i.e.,sliding in the radial direction within a layer is possible in the sealring. For this purpose, claw-like projections can be formed by piercingthe metal lamellae before they are joined to the soft material lamellae.The height of the resulting projections corresponds to approximately thethickness of the adjacent soft material lamellae.

Alternatively, the relative sliding between adjacent layers of thesealing ring may be reduced by forming step-like flanges in the metallamellae close to the inner diameter of the seal ring. Such flangesextend about the entire circumference of the seal ring and have a heightthat is at least two thirds of the thickness of the abutting softmaterial lamellae. The flanges restrict the radially freely extendingsliding layer to at most one third of the thickness of the soft materiallamellae thickness, ensuring seal integrity and proper operation of theassociated valve.

At least one of the sealing rings preferably consists of multipleannular expanded-graphite soft material lamellae interposed betweenannular metal lamellae and having PTFE rings disposed on the two sealring end faces. The PTFE rings have a stripping or wiping edge forbearing against the valve member. The stripping edges wipe small andvery small graphite particles from the valve member surface as it isaxially displaced. The inside edges of the metal lamellae provide astripping action for coarse graphite particles. The PTFE stripping edgemay be formed as a stripping lip.

The seal rings may comprise a compressed stack of alternating metal andsoft material lamellae rings. The metal lamellae rings are punched froma metal sheet such that claw-like projections extend from both sides.The claw-like projections penetrate the soft material lamellae ringsdisposed on either side of each metal ring when the stack is compressed.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may be better understood and its numerous objectsand advantages will become apparent to those skilled in the art byreference to the accompanying drawings wherein like reference numeralsrefer to like elements in the several figures and in which:

FIG. 1 is an cross-sectional, side elevation view of a shut-off valve inaccordance with the invention;

FIG. 2 is an enlarged side elevation view, partly in section, of a firstseal ring for the shut-off valve of FIG. 1;

FIG. 3 is a view similar to FIG. 2 of an alternate embodiment of thefirst seal ring of the value of FIG. 1;

FIG. 4 is an enlarged view of area A of FIG. 1;

FIG. 5 is an enlarged side elevation view, partly in section, of asecond seal ring for the shut-off valve of FIG. 1; and

FIG. 6 is a view similar to FIG. 5 of an alternate embodiment of thesecond seal ring of FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to the drawings, wherein like numerals represent likeparts throughout the several figures, a shut-off valve in accordancewith the present invention comprises a lower casing or housing 1 whichdefines a flow channel 1' and an actuator receiving bore 11. The valvefurther comprises an upper casing 6, a piston or valve member 3, a drivespindle 4, a rotatable actuator 7 and first and second seal rings whichare indicated respectively at 2 and 10. In the closed position, as shownin FIG. 1, the flow channel 1', i.e., the fluid path between housingdefined inlet and outlet ports, is closed by means of the piston 3. Thepiston 3 is axially displaceable from the closed position in which it isshown to an open position by means of imparting rotation to the spindle4. The spindle 4 is axially movable in bore 11 by means of a threadedcoupling 5 which interconnects the upper casing 6 to the valve actuatoror handle 7. A tubular expansion 6' of the upper casing 6 is coaxiallyreceived within the lower casing bore 11. The upper casing 6 is firmlymounted to the lower casing 1 by means of stud bolts 8. The bore 11receiving the first, i.e., the lower, and the second, i.e., the upper,sealing rings. Bore 11 also receives a cage-type spacer 9. Spacer 9extends between, and both locates and supports, the sealing rings 1 and10.

As shown in FIG. 2, the first seal ring 2 is built up from alternatingrings of soft material lamellae 20 and metal lamellae 21. The softmaterial lamellae 20 are preferably composed of expanded graphite. Eachof the metal lamellae 21 is provided with an axial deformation in theform of a flange 28. The flanges 28 are concentrically arranged adjacentto the shell surface 22, i.e., the ring surface which contacts thepiston 3, and have a height at least equal to two thirds of thethickness of the adjacent soft material lamellae 20. The flanges 28 thusrestrict the thickness a of the freely extending, i.e., the potentiallysliding, soft material layer to at most one third of the thickness ofthe soft material lamellae 20. The first seal ring 2 has soft materiallamellae 20 on the oppositely disposed seal ring end faces 23, 24.

The alternative embodiment shown in FIG. 3 has metal lamellae 25 withregularly arranged penetrations 26. The metal tips produced in thecourse of forming the penetrations extend through the entire thicknessof the soft material lamellae 27 arranged on either side. Such metallamellae 25 are manufactured from a metal sheet web which already hasregularly arranged penetrations 26 in the form of claw-type projections29 extending to both sides of the metal sheet. In the course of formingthe sealing rings, a web of expanded graphite is rolled into contactwith both sides of the metal lamellae 25. Rolling the expanded graphiteinto contact with the metal lamellae 25 causes the claw-type projections29 to completely penetrate the expanded graphite. Additionally, rollingpreferably increases the expanded graphite density from an initialdensity of 1 g/cm³ to a final density of 1.3 g/cm³. Sliding softmaterial layers cannot form in a first seal ring 2 manufactured in thismanner, precluding destruction by explosive medium shock.

The manufacture can, however, also be carried out according to themethod described above from rings consisting of metal lamellae 25 coatedon one side with an expanded graphite lamella 27. The seal ring iscompressed during final assembly, driving the claw-type projections intothe adjoining soft material lamellae 27 and increasing the expandedgraphite density to greater than 1.6 g/cm³ to produce a particularlyintimate bond.

As shown in FIG. 5, the second seal ring 10 may be comprised ofalternating layers of expanded graphite soft material lamellae 20 andmetal lamellae 21. An axial deformation in the form of a flange 28 ismade on each of the metal lamellae 21. The flanges 28 are concentricallyarranged adjacent to the seal ring contact surface which faces thepiston 3. Flanges 28 have a height at least equal to two thirds of thethickness of the adjacent soft material lamellae 20. Therefore, theflanges 28 restrict the thickness a of the freely extending sliding softmaterial layer to at most one third of the thickness of the softmaterial lamellae 20. The second seal ring 10 may be manufactured in thesame manner as the first seal ring 2.

The upper and lower end faces 23 and 24 respectively of the second sealring 10 may be faced with a ring 14 of polytetrafluoroethylene (PTFE).The PTFE ring 14 defines an impermeable covering ring and an annularstripping element. A lip-shaped wiping element 15 bears against thepiston 3. During operation, the wiping element 15 wipes small and verysmall graphite particles off of the piston 3. Preferably, the thicknessof each of the two PTFE rings 14 is about 1 to 2 mm, while the thicknessof the second seal ring 10 is a multiple thereof.

The alternative embodiment of the second seal ring 10 shown in FIG. 6has metal lamellae 25 with regularly arranged penetrations 26. The metaltips thus produced penetrate the entire thickness of the soft materiallamellae 27 arranged on either side. The manufacture of such a secondseal ring 10 can be carried out in the same manner as the first sealring shown in FIG. 3. Alternatively, a second seal ring 10 may bemanufactured according to the method described above from ringsconsisting of metal lamellae 25 coated on one side with an expandedgraphite lamellae 27.

While preferred embodiments have been shown and described, variousmodifications and substitutions may be made thereto without departingfrom the spirit and scope of the invention. Accordingly, it is to beunderstood that the present invention has been described by way ofillustration and not limitation.

What is claimed is:
 1. A shut-off valve comprising:a casing defining aflow channel and an actuator receiving bore; a valve member housed insaid casing, said valve member being axially displaceable relative tosaid bore for closing said flow channel; and first and second seal ringsdisposed within said casing, said first seal ring cooperating with saidvalve member to seal said flow channel, said second seal ringcooperating with said valve member to seal said bore, said first andsecond seal rings each having top, bottom, inside and outside surfaces,said first and second seal rings each comprising radially extendingmetal lamellae arranged between soft material lamellae, each of saidlamellae having a top and bottom surface and a thickness, said softmaterial lamellae having a non-homogenous structure, said metal lamellaehaving, at least in the region adjacent said inner surface, axialdeformations which establish a positive mechanical connection with softmaterial lamellae, whereby soft material sliding layers in said lamellaeare restricted to at most one third of said soft material lamellaethickness.
 2. The shut-off valve of claim 1 wherein each of said sealring metal lamellae has regularly distributed claw-type projectionsextending from said top and bottom surfaces, said projectionspenetrating into said soft material lamellae at least two thirds of saidsoft material lamellae thickness.
 3. The shut-off valve of claim 2wherein said projections penetrate said soft material lamellaesubstantially the entire thickness thereof.
 4. The shut-off valve ofclaim 1 wherein each of said metal lamellae has a circumferentialstep-like flange adjacent said seal ring inner surface, said flangehaving a height equal to at least two thirds of said thickness of saidsoft material lamellae.
 5. The shut-off valve of claim 1 wherein saidsecond seal ring soft material lamellae are comprised of expandedgraphite, said expanded graphite lamellae being separated by interposedmetal lamellae, and wherein said second seal ring further comprises apair of wiper rings comprises of a material having a low coefficient offriction, said wiper rings being arranged on said top and bottom sealring surfaces, said wiper rings each having a stripping edge for bearingagainst said valve member.
 6. The shut-off valve of claim 5 wherein saidstripping edges are formed on a stripping lip.
 7. The shut-off valve ofclaim 5 wherein said wiper rings are mounted on said top and bottom sealring surfaces.
 8. The shut-off valve of claim 5 wherein said metallamellae are anchored in adjoining of said soft material lamellae. 9.The shut-off valve of claim 8 wherein said metal lamellae are anchoredin said wiper rings.